#!/usr/bin/perl

$/ = "</Root>\n";  # let's read whole structures

while (<>) {
    my $chk = $_; # make a copy that we can muck with

    $chk =~ s{</?\w+/?>}{}g; # remove known "good tags" patterns
    my $prob = ( $chk =~ /[<>]/ ) ? 'stray angle bracket(s)' : '';

    $chk =~ s{\&\w+\;}{}g; # remove known "good entities"
    $prob .= ' stray ampersand(s)' if ( $chk =~ /\&/ );

    print "Record $. has $prob:\n$_" if $prob;
}

##</code><code>##

# perl 1-liner to output one "tag" per line:

perl -pe 's{^.*?<}{}; s{>[^<]*}{>\n}g;' file.xml | sort | uniq -c